Chables pinder and william a



(No Modem G. PINDER 8!. W. A. HARDY.

Screen Plate for Paper Machines.

NO. 2395837. I Patented April 5,1881.

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g @IN VEN TIJRS Mamie, ,g /fomh r m v PETERS, PHOTD-LITHOGRAPHER.WASHINGTON! Dv UNIT D STATES PATENT OFFICE.

CHARLES FINDER AND VILLIAM A. HARDY, OF FITGHBURG, MASS.

SCREEN-PLATE FOR PAPER-MACHINES.

SPECIFICATION forming part of Letters Patent No. 239,837, dated April 5,1881.

Application filed March 7, 1881. (No model.)

To all whom it may concern Be it known that we, CHARLES FINDER and\VILLIAM A. HARDY, of Fitchburg, county of Worcester, and State ofMassachusetts, have invented an Improvementin Screen-Plates forPaper-Makin g Machines, of which the following description, inconnection with the accompanying drawings,-is a specification.

Our invention relates to screen-platesfor paper-makin g mechanism, andhas for its object to increase the screenage-surface of the plate, andat the same time cheapen its construction.

Screen-plates as commonly constructed are made of rolled brass aboutthree-eighths of an inch thick, this thickness being required to giverequisite strength. The said plates are milled out at their undersurface, the milling-tool forming a series of channels extending nearlythrough the plate-to its upper sur face, which is then sawed throughinto the said channels, thus forming a series of slits, through whichthe pulp passes. It is requisite that these slits shall remain ofthesame width, in order to effectively screen the pulp, and the ridgesof metal between the milled channels are left to form a sufficientsupport for the plate and pulp thereon, as described ina form er patentgranted to us, N 0. 234,719, dated November 23,1880, to which referencemay he had. It has been found in practice that these slits and milledchannels, when cut in a single homogeneous plate in the usual manner,cannot be made more than three or four inches long without so weakeningthe portions of the plate between the said channels as to render themliable to be sprung out of place under the action of the superincnmbentpulp. These channels have consequently been made of the above-mentionedlength, and several se- .ries of them placed end to end in the sameplate. 4

Owing to the nature of the milling-tool employed the upper surfaces ofthe channels are curved from the under side of the plate toward theupper side, so that the said channels, near the upper surface of theplate,where sawed through to make the screening-slits, are much shorterthan at the under side, and a considerable screenage-space is lostbetween each series of channels and slits.

We have discovered in our experiments in the construction ofscreen-plates that when the channels and slits are made longer thanabove described the portions of the plate between them become laterallydisplaced, making some of the slits wider than they should be, andwholly closing up others, but that there is no appreciable yielding in adownward direction under the weight of the superincnmbent pulp.

Our invention, in accordance with this discovery, consists in making themilled channels several times longer than heretofore prae,

ticed, extending them entirely across the plate, if need be, anddividing the sawed slits longitudinally into a series of short slits(about the usual length) separated by a narrow portion of unslittedmetal, which serves to bind the strips of metalbetween the slits andchannels together, and prevent lateral displacement thereof. This smallportion of metal between the bottom of the channel and upper surface ofthe plate performs the function of the portion formerly left between theadjacent series of channels, which extended from the nnderto the uppersurface of the plate, and by the present plan the unslitted portionbetween the different series of slits is much shorter than formerly, andthe scrcenage area consequently increased.

Figure l is a plan view of a screen-plate constructed in accordance withour invention; Fig. 2, an under-side View of a portion thereof on alarger scale Fig. 3, a longitudinal section of Fig. 2, on a planepassing through the slits, the dotted lines indicating the form ofcutting-tools and a plate as commonly constructed; and Fig. 4 is atransverse section thereof.

The plate a may be of any desired dimensions and material, it beingshown as a section of a plate to be mounted in a holding-frame, asdescribed in. a former patent to us, No. 226,545, dated April 13, 1880.

The plate a is provided with 'a series of channels, b, formed by asuitable milling-tool, 0, (see dotted lines, Fig. 3,) in its underportion, and extending nearly through to its up per surface, as shown.The upper portion of the plate is then cut through by a saw, 01, (seedotted lines, Fig. 3,) forming a series of fine slits, 6, extendingthrough from the upper surface of the plate into the channels I), formedby milling-tools. The ribs f, of the material of the plate that are leftbetween the said channels I), serve as a support for the portions t ofthe upper part of the plate between the slits e in Fig. 1 and the pulpsustained thereon. It has been found in practice that when thesechannels]; and slits a (one to each of the said channels 1)) are madeaboveacertain lengthsay three or four inehes-the portions fi of theplate between the said channels and slits are not sufliciently rigid,andbecomebent out of shape as the plate is used. The plates haveconsequently been milled and sawed, as shown in dotted lines, Fig. 3,making several series of the said channels, placed end to end, andleaving the metal at 2 untouched.

In a sectional plate of a size shown in the drawings there would have tobe two such series of channels, in order to afford the requisiterigidity, and when the plate is not made in sections there would beseveral such series in its whole surface.

In our invention the channels b are made to extend from one to the otherside of the plate; but the slits 0, instead of extending the entirelength of the channels, as before, only extend for a length about thesame as that-of the channels as formerly constructed, a portion of uncutmetal, m, being left between the different slits e, that correspond toeach one of the channels I). By this method of construction the ribs fbetween the channels are found to be sufficiently strong to properlysupport the overlying strip 1' of the upper portion of the plate and thepulp thereon, while the uncut portions m of the upper part of the plateprevent the lateral yielding or displacement of the strips f t, whichwould take place if the slits 0 extended the entire length of thechannels b when extended entirely across the plate, as described, andthe said stripsfi were rigidly held only at the end of the saidchannels.

As the effective length of a slit, 6, for screenage is only the distancebetween the points 3 when the saw-cut intersects the channel made by themilling-tool, it will be seen, referring to Fig.3, that the said lengthis considerablyincreased by the removal of the metal at 2,which, by theformer methods,was deemed necessary to perfectly sustain the strips 1'.

In large plates it may not always be desirable to extend the channelswholly across the plate; but two or three or any desired number ofseries may be employed without departing from our invention, the saidchannels being longer than usual, and each connected with two or moreslits separated by a portion of unsawed metal.

We claim- 1. As an improved article of n1anufacture,a screen-plateprovided with a series of channels, 1), extending wholly across and intothe said plate, from its under to its upper surface, and with twoor moresawed slits extending from the upper surface of the plate through intoeach of the said channels, a portion of metal being left unsawed betweenthe different slits in connection with one and the same channel,substantially as and for the purpose set forth.

2. In a screen-plate, the channels I), extending in from'one surfacethereof, and two or more sawed slits, 6, extended through from the othensurface of the plate into each of the said channels I), combined withthe unsawed portions 121 of the said plate between each pair of slitsand the corresponding ehaunel,whereby the strips of metal left betweenthe adjacent parallel channels and slits are prevented from yieldinglaterally to open some of the said slits and close others, substantiallyas described.

In testimony whereof we have signed our names to this specification inthe presence of two subscribing witnesses.

CHARLES FINDER. WVM. A. HARDY. Witnesses E. B. RooKwooD, J 0s. P.LIVERMORE.

